As per the PMBOK guide , one of the outputs of the Plan Communications management is Project documents updates , it is quite understandable that we might end up updating the stakeholder register but there is another document which gets updated and it is the PROJECT SCHEDULE, will apreciate if some light is thrown on it as to how this document is relevant here, the answer will help to connect the dots.

I think Project Schedule can be updated in case of clients/stakeholders request for a weekly/biweekly or any other status report for which we didn't plan while creating project schedule. In this case, this document can be updated.

Again, I would request admin or seniors to review my answer and confirm this.